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EXPERIMENTS in 

STRENGTH OF MATERIALS 
and CEMENT LABORATORY 



By EARL B. SMITH, M. E. 




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EXPERIMENTS 



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Strength of Materials 

and 

Cement Laboratory 



BY 
EARL B. SMITH, M. E. 

Assistant Professor of Experimental Mechanical Engineering 



Drexel Institute, Philadelphia 
1911 






/^O,^^ 



Copyright 1911, by 
Earl B. Smith 






Printed by 

THE INSTITUTE PRESS 

DREXEL INSTITUTE 
PHILADELPHIA 



'CI.A2971e58 



STRENGTH OF MATERIALS LABORATORY 



In the theoretical consideration of the strength of materials, 
all bodies are considered to be perfectly rigid; that is, the points 
and parts of any material are considered to be always in the same 
relative position to each other. But since this assumption is not 
true for materials of construction, and that no material is ab- 
solutely rigid, the mathematical study of the strength of ma- 
terials is not alone sufficient to gain the knowledge required for 
the rational designing of machines or structures. The behavior 
of materials under stress must, therefore, be observed and un- 
derstood, as well as the physical properties of the materials. 

Physical tests are those tests made for the purpose of observ- 
ing and studying the physical properties of the materials of con- 
struction, and the behavior of the materials while, or after, being 
subjected to stress. 

The object of tests and experiments relating to the strength 
of materials may be generalized as follows. To ascertain: (i) 
The resistance of materials to any change in form or shape. 
(2) The characteristics whereby the quality of a material may 
be determined. (3) Experimental proof of the theoretical laws 
relating to the strength of materials, that is, the general laws 
of variation in strength as affected by material, size and form. 
(4) The comparison of the strength and the behavior of ma- 
terials under different kinds and combinations of stresses. 

General Instructions 

1. When the test specimen is received it should be carefully 
inspected for flaws and imperfections of any kind, and a note 
made of them. All information accompanying the specimen 
should be recorded. The specimen should be very carefully 
measured. Usually the cross-sectional dimensions should be de- 
termined with a micrometer caliper. Be sure to measure the 
specimen before testing. 

2. The position of the specimen in the testing machine should 
always be such that the machine will be loaded centrally. In 
tension tests the specimen must be placed truly central in the 
grips, and the proper liners used back of the jaws so that the 
points of the jaws will not project more than ^" beyond the 
pulling heads. This position of the jaws is very important in 



2 STRENGTH OF MATERIALS LABORATORY 

order to prevent injury to the jaws and pulling heads, and to 
avoid any difficulty in removing the broken specimen. The jaws, 
the liners, and the bearing surface of the slots in the pulling heads 
should be cleaned of all grit and mill scale from formerly tested 
specimen, and slightly lubricated with a heavy oil or grease. 

3. When testing a ductile material or an unknown material, 
look for indications of the elastic hmit. But when the material 
is positively known to be cast iron, wood, stone, brick, cement, 
or concrete, then the elastic limit need not be looked for except 
when making some of the special tests on these materials. 

4. All data actually taken during a test, and all notes and in- 
formation relative to the specimen, the test, or the apparatus, 
must be recorded in your Laboratory Log Book. From this book 
your final report is to be written. This log book must be com- 
plete, clear and neat — it will be inspected from time to time. 

5. The scale beam should be carefully balanced at zero read- 
ing, when the specimen is in place with no load. The recoil 
nuts should bear on the rubber buffers only lightly. The mech- 
anism for moving the poise should be tried to see that it is 
working properly. 

6. When starting the machine, start the motor slowly with the 
friction clutch disengaged ; after the motor is started, engage 
the clutch slowly. Never change the speed gears zvhile the ma- 
chine is running. Don't leave the machine zvhile the motor is 
running. 

7. After each day's work all machines, apparatus, and instru- 
ments must be cleaned and returned to their proper places, and 
inspected by the instructor before you leave. 

8. The assignments for each day's work will be made in ad- 
vance. All laboratory outlines and all references pertaining to 
the assigned work must be read in advance of the work. A 
student may be excluded from the laboratory- work of the period 
for lack of preparation. 

9. The speed of the testing machine should be such that, the 
pulling head will move at the rate of 0.02 to 0.03 of an inch per 
minute for tension and compression tests up to the elastic limit; 
above the elastic limit about 0.3 of an inch. For transverse tests 
from 0.03 to 0.05 of an inch per minute, depending upon the 
span and the material. 

THE WRITTEN REPORT.— E^ich experiment must be writ- 
ten up separately and completely, and included in a manila cover ; 
all securely fastened together with brass fasteners. 



STRENGTH OF MATERIALS LABORATORY 3 

Only standard size report paper may be used (8'' x lO}^''). 
Curves must be plotted only on standard cross-section paper. 

When formul?e are used, the meaning of each term must be 
given. All numerical substitutions in a formula must be given 
in full, and in the order of the terms as first shown. Numerical 
reductions may be omitted. In general, the result need not show 
more than four significant figures, since that is usually within the 
limit of errors in the observed data. Your results should ap- 
proximate the average representative values for such tests and 
materials ; if not, look for the cause of the variation : 

Curve. The curve usually plotted in connection with strength- 
of-materials tests is one which shows the relation between the 
load on the specimen and the deformation which this load in- 
duces. It is usually called the stress-strain diagram. The curve 
is plotted with loads in pounds per square inch as ordinates, and 
with unit deformation in inches as abscissae ; however, the curve 
is sometimes plotted with total load vs. total deformation. 

The curve sheet must be a complete summary of the test. It 
must show the character of the test and what results have been 
obtained. The curve sheet must be clear and complete without 
the reader having to make any reference to other parts of the 
report. 

All points locating a curve must be shown by a small circle, 
a cross, or a circle enclosing some mark. The curves must be 
drawn in ink with some sort of curved ruler. Use medium fine 
lines. In this work all curves are smooth curves. 

The curve sheet must bear a neatly lettered title, stating the 
character of the test, the material, the original dimensions, the 
date, and your name. In some cases an explanatory note is neces- 
sary to make the curve sheet clear and independent of the writ- 
ten report. 

Experiment A. Universal Testing Machine 

References : Johnston's ^Materials of Construction, arts., 259, 
270, 271 ; ]\Ierriman's Mechanics of ^Materials, arts., 168-170; 
Olsen's Catalog A, pp. 34-40. 

1. Be able to designate and explain the purpose of each part 
of the machine. Xote particularly the parts which constitute 
the frame and base of the machine, and the parts which rest upon 
the weighing mechanism. 

2. Follow out the transmission of motion from the motor 
pinion to the moving cross-head, noting the scheme for changing 



4 STRENGTH OF MATERIALS LABORATORY 

the Speed of the cross-head independently of the speed of the 
motor. Note under what conditions the positive clutch may be 
engaged. 

3. What is the pitch of the straining screws? Engage the 
clutches for tlie highest speed of the cross-head ; at this speed 
determine the number of revolutions of the main shaft neces- 
sary to move the cross-head i inch. This should be done by 
determining the ratio of the gears, then checked by trial. Note 
the number of straining screws, and whether they revolve in ap- 
plying the load or large nuts are revolved on the screws. 

4. With the motor running at the slowest speed, run the crOss- 
head up and down, and determine the speed of the cross-head in 
inches per minute for each of the four speed changes. This 
should be done for several inches of cross-head movement. 

5. Note the method of driving the poise, and how it is ac- 
complished without effecting the balance of the beam. Weigh 
the poise. With the poise at the highest graduation compute 
the total multiplication of the system of weighing levers. Make 
a plan and elevation sketch showing the levers and knife edges 
of the weighing system. 

6. With the beam exactly balanced at zero reading, determine 
the weight necessary on the compression bed to appreciably raise 
the beam. Place a wood block in the machine and exert on the 
block pressures equal to Yx, y2, %., and full capacity of the 
machine; at each of these loads determine the additional weight 
on the compression bed necessary to appreciably raise the beam. 
Tabulate these results in the proper place in data form No. i. 

7. By trial determine the maximum and the minimum sizes of 
round and flat tension specimens that may be gripped in the 
jaws. The jaws may be yi inch inside the surface of the cross- 
head, or projecting % inch outside. 

Experiment B. Torsion Machine 

Determine the speed ratio between the power or belt pulley 
and the revolving chuck of the machine ; this should be done by 
counting the teeth in the gears. 

Make a diagramatic sketch of the weighing mechanism. 
Weigh the sliding poise, and compute the total multiplication of 
the weighing levers. Note that loads in torsion are weighed in 
inch-pounds. 

Sketch the scheme of fastening the specimen in the chucks, 
and determine the maximum size of round specimens that may 
be used in the chucks. 



STRENXiTH OF MATERIALS LABORATORY 5 

Experiment i. Commercial Tension Test 

References : Johnson's IMaterials of Construction, arts., 264- 
267; IMerriman's Mechanics of Materials, art., 171; Cambria 
Steel Co's Handbook. ''Specifications for Steel." 

A commercial tension test is one made to determine the qual- 
ity of a material, and whether the material will satisfy the 
specifications of the customer. In a commercial test the value 
obtained for the elastic limit is usually that value of the stress 
near the yield-point ; in fact, there is often no distinction made 
between elastic limit and yield-point. 

1. The materials to be used are wrought iron and steel. The 
specimen must be carefully inspected and measured. Mark an 
8-inch gage length on the specimen by making two centre punch 
marks symmetrically about the middle section. 

2. Place the specimen in the machine, observing the instruc- 
tions under "General Instructions," (2). Chalk the surface of 
the specimen near the upper gage mark. Before continuing, have 
the instructor inspect your work and the apparatus. 

3. Run the machine at next to the slowest speed. The elastic 
limit (in reality the yield-point) is to be determined in the fol- 
lowing three ways : 

(a) By a pair of sharp dividers, place one joint of a pair of 
dividers in the lower gage work, then, with dividers set to gage 
length, and while load is being applied make marks with the 
other divider joint on the chalked surface of the specimen. The 
elastic limit is indicated when there is an appreciable increase in 
difference between succeeding lines. 

(b) By reading the load at the instant of the drop of the 
scale beam. This will necessitate care in always keeping the 
beam balanced. 

(c) By noting the load when the mill scale begins to fall 
from the specimen. 

All observers will have to be alert, for these readings may be 
close together, and occur very quickly. 

4. After the elastic limit is passed run the machine at the 
next higher speed ; continue the test until the specimen is broken, 
being careful to read the maximum load which is the ultimate 
load on the specimen. 

5. After rupture, remove the broken pieces from the machine 
and lay them together and measure the elongation between the 
gage marks to the nearest o.oi of an inch. Measure the dimen- 
sions of the cross-section at the point of fracture. 



6 STRENGTH OF MATERIALS LABORATORY 

6. By reference to standard specifications for steel, classify the 
material of each test. 

Report. Fill out the standard data sheet furnished. Plot 
curves with Per Cent Carbon as abscissae, and, as ordinates, a 
Unit Elastic Limit ; h Unit Ultimate Stress ; c Per Cent. Reduc- 
tion of Area ; d Per Cent. Elongation. Describe and sketch the 
appearance of the fracture in each case. 

Experiment 2. Complete Tension Test with Extensometers 

References: Johnson's Materials of Construction, arts., 12-16, 
274, 365; Merriman's Mechanics of Materials, arts., 4; Car- 
penter's Exp. Eng., art., 96. 

1. Use the Henning Extensometer for determining the elonga- 
tion of the specimen during the test. Sketch and briefly de- 
scribe this instrument in the report. Be particular about the 
alignment of the extensometer and its position on the specimen. 
Apply a load of about 500 pounds to the specimen and make 
the final adjustments of the extensometer. Then remove the 
load and take a zero reading. Have an instructor inspect the 
apparatus before continuing. 

2. Run the testing machine at the slowest speed. Estimate 
approximately the load at elastic limit, then apply increments of 
load equal to about o.i of this. At each load read the elongation. 
When near the elastic limit and for a few loads past, make the 
load increments rather small, so the points on the stress-strain 
diagram will be close together. 

Take a few more loads and extensometer readings up to the 
maximum load, then remove the extensometer to prevent injury 
to it when the specimen breaks. Continue the test, at medium 
speed of the machine, to rupture. After removing the extenso- 
meter, elongations for a few loads are to be determined with a 
pair of dividers in the gage marks. 

Note : All readings for elongation must be taken very quickly ; 
for the specimen continues to stretch slightly after the machine 
stops. Keep the set screws of the extensometer tight, but do 
not force them. 

4. To determine the modulus of elasticity take the elongation 
between two loads below the elastic limit ; and not from zero load 
to elastic limit. Possibly between o.i and 0.8 of the elastic limit. 

Report. Plot a stress-strain diagram of the complete test, 
using a scale such that the curve will well fill the sheet of stand- 
ard cross-section paper, and be easily read. Eill out the standard 
data sheet furnished. 



STRENGTH OF MATERIALS LABORATORY ^ 

Experiment 3. Distribution of Elongation 

Reference: Johnson's Z^Iaterials of Construction, art., 361. 
. I. On the specimen assigned, lay ofif ver}^ carefully 9 gage 
marks i inch apart. Test the specimen in tension at the slowest 
^pee ]. At small increments of load determine the elongation 
at each i inch gage length. The gage lengths may be designated 
by o-i. 1-2, 2-3, etc. 

Report. For each gage length, and the total gage length plot 
a curve (nine in all) ; Total Load vs. Elongation. See specimen 
curve, posted. Use the standard data sheet furnished. 

Experiment 4. Shear Tests 

Reference: ]\Ierriman's ^Mechanics of ^Materials, art., 15. 

I. The specimen for testing will be wood (cross-grain), wrought 
iron, steel and cast iron. Each piece must be firmly clamped in 
the shearing block so as to prevent bending. The test will be in 
double shear, but results must be reported as single shear, ?". e., 
one-half of double shear. 

Report. ]\Iake sketches and describe the character of the 
breaks. Use standard data sheet. 

Experiment 5. Shear and Tension 

References : Johnson's ^laterials of Construction, arts., 298- 
3C0, 374; IMerriman's ]^Iechanics of ^laterials, arts., 6. 

1. The specimen for testing will be long enough so that a 
shear test may be made from one end ; then the remainder of the 
specimen is to be tested in tension. An instructor must inspect 
the work before machines are started. 

2. The shear test will be in double shear, from which the re- 
sults for single shear are to be obtained by dividing by two. The 
ultimate strength in shear is all that need be determined. The 
tension test is to determine the ultimate strength, the elastic 
limit and elongation. 

Report. The data and results are to be tabulated in the stand- 
ard data sheet furnished. The report must describe the method 
and special apparatus with sketches. Give your conclusions as 
to what the results of the tests seem to show. 

Experiment 6. Compression Tests 

References: ^lerriman's Strength of ^Materials, art., 18; John- 
son's ^laterials of Construction, arts., 17-18, 21, 200, 278-283. 



8 STRENGTH OF MATERIALS LABORATORY 

1. The length of a specimen for a pure compression test should 
be about 4 times the smallest cross-section dimension. The 
specimen should be placed truly central in the testing machine ; 
and the machine should be run at its slowest speed. Sketch and 
describe the compression micrometer which you use. 

2. Estimate the probable elastic limit and apply loads equal 
to about 1/5 of this, and at each load measure the amount of 
compression. Take a few extra loads of smaller increments when 
near the elastic limit. Continue the test to rupture ; or, until a 
maximum load is reached ; or, until the load starts on an unlimited 
increase. 

Report. Determine from your data the modulus of elasticity 
in compression. Plot a curve : Unit stress vs. Compression. 

In your report explain carefully any peculiarities and difficulties 
of the test, and discuss briefly the reliabiHty and correctness of 
your data and results. Use standard data sheet. 

Note: Protect yourself from flying pieces of the specimen 
when testing brittle material. 



Experiment 7. Ultimate Strength in Compression (Metal, 
Stone and Brick) 

1. The specimen should be carefully centered in the testing 
machine, and the test conducted with machine running at the 
slowest speed. 

2. The materials to be tested will be cast iron, wrought iron, 
steel, stone and brick. When making stone or brick tests the 
bearing surfaces are to be imbedded in plaster-of-paris ; or there' 
should be placed three thicknesses of blotting paper both above 
and below the specimen. For the other materials the load may 
be applied directly to the bearing surface. Use standard data 
sheet. 



Experiment 8. Transverse Tests (Wood) 

References : Merriman's Mechanics of Materials, arts., 19, 52, 
55> 56; Johnson's Materials of Construction, arts., 197-199; 
Tables XLVIII, LI. 

I. Carefully center the beam in the testing machine and apply 
the load at the center between the supports. Adjust the deflecto- 
meter in such a manner that deflections will be measured from 



STRENGTH OF MATERIALS LABORATORY 9 

the original to the existing position of the neutral line. The 
deflections should not be measured from the bed of the testing 
machine to the middle load bearing, nor to the under side of the 
beam ; measurements thus taken include any compression or 
crushing there might be at the bearing points. 

2. Apply small equal increments of load, equal to about o.i of 
the computed load at elastic limit, until failure occurs. At each 
load, carefully determine the deflection. Watch closely for the 
hrst indication of failure in either the upper or lower fibers, note 
the character of this first sign of failure, and the load at which 
it occurs. 

3. Cut from the section near the break a piece of the wood 
of from 3 to 4 cubic inches, weigh carefully on chemical bal- 
ances and place in the drying oven. At the next period weigh 
again and determine the percentage of moisture. Determine also 
the specific gravity of the dry wood. 

Report. Compute the maximum fiber stress at elastic limit, 
the modulus of elasticity, and the modulus of rupture. In your 
report sketch and describe the method and character of the fail- 
ure of each specimen. Plot a curve for each test: Load vs. 
Deflection. Describe fully the method of measuring the deflec- 
tions, and how the specific gravity was determined. Use standard 
data sheet. 

Experiment 9. Transverse Test (Cast Iron) 

References : Alerriman's Mechanics of ]\Iaterials, arts., 52, 55, 
56, 121; Johnson's Materials of Construction, arts., 288-290, 350; 
Table XXIV. 

1. The specimen to be used will be long enough for a test 
length or span of 12 inches. The specimen must be carefully laid 
off for the position of the load and supports ; and then centered 
in the machine, so load will be applied exactly at the middle 
section. The cross-section is to be measured to the nearest o.oi 
of an inch at the middle section. 

2. The deflectometer is to be carefully set and adjusted for 
properly determining the deflection. Run the machine at a slow 
speed. Appl}^ increments of load of 200 pounds, and at each 
load determine the deflection. Continue the test to rupture. 

Report. Plot a curve of Load vs. Deflection. Use this curve 
for the necessary values for computing the modulus of elasticity, 
of rupture, and of resilience. Use standard data sheet. 



10 STRENGTH OF MATERIALS LABORATORY 

Experiment lo. Torsion Test 

References : Johnson's Materials of Construction, arts., 27-29, 
301, 302; Merriman's Mechanics of Alaterials, arts., 6, 15, 89, 

90, 93. 94. 

1. The.Olsen Torsion Testing Machine. Carefully balance the 
beam. Insert the specimen in the chucks as far as possible. The 
front ends (marked F) of the wedges must all be towards the 
outside of the chucks. The adjusting screws in the chucks must 
all be set exactly alike, so as to center the specimen. Apply a 
small load of about 200 inch-pounds to the specimen so as to set 
the wedges ; then release this load. 

2. Apply the arms to the specimen at the gage marks, for 
reading the angle of twist. Adjust the arms to the proper length, 
so that the center of the specimen will be such a distance from 
the flexible steel scale that the decimal divisions will be a con- 
venient part of a degree. Also these arms should be so placed 
that they will engage with the projections on the pointers of the 
dials on the chucks. These dials on the chucks are for determin- 
ing the total twist of the specimen between the gage marks. 

3. Test at a very slow speed. Keep the beam well balanced 
and take readings of the angle of twist about every o.i of a 
degree until about four readings are taken beyond the elastic 
limit. Now run the machine at fast speed and continue the test 
till rupture occurs, observing the total number of turns. 

Report. Compute the unit shearing stress at elastic limit and 
ultimate; the shearing modulus; and the unit elongation in the 
outer fiber. Plot a curve showing your results, with Load in 
inch-pounds as abscissae, and Angle of Twist as ordinates ; the 
scale may be changed after passing the elastic limit. 

Experiment 11. Autographic Tension Test 

References : The Olsen Catalog A, p. 35. 

The Autographic Apparatus on a testing machine is for the 
purpose of automatically drawing the ''Load vs. Deformation'' 
curve on a sheet of cross-section paper. 

1. Follow out all the parts and connections of the autographic 
apparatus, and be prepared to explain its action in transmitting 
only the deformation of the specimen and why it does not trans- 
mit any motion of the specimen due to slipping in the jaws. 
Make a diagramatic sketch of the whole apparatus from the 
fingers to the recording drum. 

2. Insert a specimen on which you have placed the aluminum 



STRENGTH OF MATERIALS LATlORATORY 11 

clamps. Apply a small load sufficient to set the wedge grips in 
position, and then release. Adjust fingers to the clamps, place 
paper on the drmii. adjust the pencil, depress the right hand beam 
key and run the machine at slowest speed. x\fter passing the 
elastic limit change to faster speed, depress the left hand key 
and continue to rupture. Note during the test the position of 
the pencil and the scale beam reading, so as to determine the 
scale of the curve. Keep the clamps tight on the specimen. 
After finishing the test complete the diagram by adding the 
necessary label, notes, and scale. 

Experiment 12. Wood Columns 

References: iNIerriman's ]^Iechanics of Material, arts., 80, 81. 

84- 

1. The columns are to be made from the same piece of timber. 
Two long columns will be provided ]/s^^ x 2'' x 20'' ; after these 
have been tested, as indicated below, they are to be sawed to the 
shorter lengths. 

2. For the tests with round ends set the 20'' column centrally 
in the testing machine between the knife-edge bearing blocks. 
With a rubber-band place a steel scale on the column crosswise 
at the middle section, and stretch a fine thread lengthwise along 
the neutral axis. Apply a small load, noting the amount when 
bending occurs. Note the direction (right or left) and amount 
of the deflection on the steel scale. Release the load, and with 
centering screws readjust the knife edges so as to cause bending 
in opposite direction. Apply the same load as before, and note the 
deflection. In this manner continue to load and adjust knife 
edges until the load seems to be applied truly along the axis of 
the column, and when a slight adjustment of the knife edges 
will change the deflection to the opposite side. Now apply loads 
to produce deflections in increments of about 0.03'' until a very 
slight increase in load will produce a comparatively large increase 
in deflection. But don't continue the deflection of the 20'' 
column beyond 0.25''. 

3. Remove the 20" column after test and cut it to 17'' and 
test as before. Likewise continue to cut off 3'' each time until 
a 11'' column is tested. 

4. For the tests with fixed ends, clamp the foot clamps to 
each end of the column. Then, beginning with the 20'' column, 
proceed as indicated in paragraphs 2 and 3 above. 

Report. For each kind of column plot a curve with 1/r as 



12 STRENGTH OF MATERIALS LABORATORY 

abscissae and maximum load as ordinates, draw a straight line 
through the points. Also for the long column of each kind plot a 
curve of Load vs. Deflection. 

Experiment 13. Ultimate Strength in Compression (Wood) 

Test three pieces of each kind of assigned wood under each 
of the following conditions : 

1. Wood in the condition received, that is, air dried, applying 
the load on end of grain. 

2. Same as i, except apply load on side or across the grain. 

3. Same woods as before, except have been soaked in water 
for at least 24 hours. Test 3 pieces on end and 3 pieces across 
the grain. The dimensions of the wood blocks should be taken 
before soaking. 

Report. Show the relative strengths of the woods when dry 
and when wet. Use standard data sheet. 



CEMENT LABORATORY 



1. Xeatness is one of the most necessary requirements for 
successful work in the Cement Laboratory, Machines, apparatus, 
instruments, tables,, and, in fact, everything connected with the 
laboratory must be kept clean and in first-class condition. After 
each day's work, and before the student leaves the laboratory, 
the instructor will inspect the work and the condition of all 
apparatus used. 

2. Be very careful about allowing concrete or cement to set 
in waste cans, or on the floor or tables. Remember that it 
requires only a small amount of moisture to cause cement to set 
and harden. Posifk'cly, all cement must be kept out of sinks 
and drains; do not even ivash your hands or rubber glores in a 
zvash basin or any place zvhcre tJie cement is likely to harden and 
stop up the drain. Any violation of this rule will be just cause 
for barring the student from the laboratory. 

3. Be very careful to avoid any mixing of the difi:"erent kinds 
and brands of cement or sand in the bins. Each bin has its 
scoop, or small shovel, and it must not be transferred to another 
bin. If cement is spilled on the floor, clean it up immediately 
and throw it in the waste can. 

4. It is advisable to wear rubber gloves when mixing cement. 
The lime contained in the cement will usually attack the hands 
and make them very sore if they have not been protected. 

5. All specimens (i. e., briquettes, cubes and prisms) are to be 
placed in the damp closet for 24 hours, after which they must be 
removed from the moulds and stored under water in an assigned 
compartment of the immersion tanks until tested. 

6. All glass plates and moulds should be slightly oiled, only 
sufficient oil should be used to insure a thin film or coating over 
the surfaces. This should always be done before mixing the 
cement, and care must be taken to avoid the mixing of oil with 
the cement. A very important exception to this is the glass plates 
used for pats, which must be perfectly free from oil. 



14 CEMENT LABORATORY 

DEFINITIONS. 

Paste. This is a mixture of cement and water, before set. 

Mortar. This is a mixture of cement, sand and water. 

Concrete. This is a mixture of cement, sand, stone, and water. 

Neat and Neat Cement, are synonymous terms used to desig- 
nate a product resulting from the mixture of cement alone with 
water. It is a hard set paste. 

Set. When a paste, mortar, or concrete, is allowed to stand, 
it soon begins to lose its plasticity, and will finally become hard ; 
then it is said to have set. When the mass begins to harden, or 
is just changing from its semi-fluid and plastic state, it is termed 
initial set. When this action is complete, and the mass cannot be 
moulded without rupturing or cracking, it is termed final set. 
The mass will then continue to increase in hardness and strength, 
and this is termed hardening. 

Experiment C-A. Briquette Testing Machines 

Lever Type. i. Make a sketch of the machine, showing all 
the essential parts, including the apparatus for automatically 
operating the poise. Show on the sketch the length of all the 
levers, measured from Q(\gt to ec^ge of knife supports. 

2. Compute the total multiplication of the levers and the 
weight of the sliding poise, then check result by removing the 
poise and weighing it. Show all work and computations in your 
report. 

Shot Type. 3. Make a sketch showing all the essential parts. 
Give length of all levers. 

4. Explain the action of the shot leaving the bucket and how 'it 
causes the load to be applied to the briquette. Explain in detail 
how to calibrate the machine. 

Experiment C-i. Specific Gravity of Cement 

Reference: Standard Methods of Testing, paragraphs 8-15. 

I. Fill the Le Chatelier specific gravity flask with benzine to 
the lowest mark. Be very careful to keep the benzine away from 
any fire or sparks. The benzine should be the same temperature 
as the room. With a small glass tube or a pipette carefully adjust 
the lower meniscus to the mark, and avoid parallax in doing so. 
When handling the flask grasp it near the top, or above the level 
of the benzine, so as to avoid errors due to temperature changes. 



CEMENT LABORATORY 15 

2. Provide a glass funnel supported on a ring stand, and so 
placed that the end of the funnel will extend to about one inch 
into the specific gravity flask. Place a glass rod in the funnel 
so as to close the bottom. 

3. Weigh out very carefully 65 grams of the cement and place it 
all in the funnel. By the use of the glass rod allow the cement to 
run in a small stream into the flask. Use a small camel's hair 
brush to insure the last trace of cement entering the benzine. 
The object of introducing the cement into the benzine in this 
manner is to avoid all air bubbles. Read by estimation to the 
nearest tenth of the smallest divisions of the scale on the stem of 
the flask. Results are to be computed to the second decimal 
place. 

4. Check determinations are to be made by each of the two 
methods given in the "Standard ]\Iethods of Testing." Use 
form C-i. 

5. To clean the flask, shake it vigorously over the settling jar. 
After the cement has settled in the jar, pour as much as possible 
of the benzine off for further use. 

Experiment C-2. Fineness of Cement 

Reference : Standard ^lethods of Testing, paragraphs 16-19. 

1. Sieves Xumber 50, 100 and 200 are to be used. With a 
linen tester's microscope determine the mesh of each sieve ; that 
is, determine the number of openings per linear inch. Alake 
several determinations on each sieve at different points. 

2. Weigh out a 50 gram sample of the cement, which has 
previously been screened through a number 20 sieve to break 
up the lumps. Place the number 200 sieve in the sieve pan, and 
place the 50 gram sample on the sieve with about one hundred 
ys'^ steel balls ; then put on the sieve cover. Shake the whole for 
about 7 minutes, as specified in the "Standard ^Methods of Test- 
ing." After thus shaking, weigh the amount remaining o]i the 
sieve. Replace on the sieve and shake for one minute more. 
If more than 0.25 gram (which is 0.5 per' cent.) passes the sieve 
in this time, continue shaking for another minute, and so on. 
The sample having been thus properly and sufficiently sieved, 
weigh the residue remaining on the sieve. For the final weight 
do not attempt to weigh the amount that has passed a sieve. 
Separate the balls each time before weighing by passing the 
cement through a number 20 sieve. 



16 CEMENT LABORATORY 

3. In like manner sieve the residue remaining on the 200 sieve 
through the 100 sieve, and weigh the residue. The time required 
will be about 4 minutes. 

4. Then in like manner pass this residue through the number 
50 sieve, and weigh the remaining residue. This may require 
only a few shakes. 

5. Results should be determined and reported to the first 
decimal place. Use form C-2. 

Experiment C-3. Normal Consistency 

Reference: Standard Methods of Testing, paragraphs 23-31, 
46-52. 

1. Weigh out a 500 gram (16.6 oz.) sample of the cement, and 
mix to a paste, using about 24 per cent, of water. Cement and 
sand are taken by weight, and water by volume, in the metric 
system. This mixing of the paste must be as specified in the 
"Standard Methods of Testing," paragraph 52. 

2. Follow the method as given in the above reference, using 
the Vicat Needle Apparatus. If the percentage of water used 
does not give the standard normal consistency, make another 
paste with a greater or less amount of water, and so continue 
with different percentages of water until the required amount is 
determined which will give a normal consistency. Record each 
different trial. Use form C-3. 

Experiment C-4. Time of Setting 

Reference : Standard Methods of Testing, paragraphs 32-39. 

1. With the Vicat Needle Apparatus. With 500 g. of cement 
make a paste, using the amount of water to give the normal 
consistency as found in Experiment C-3, and place it in the ring 
of the Vicat apparatus. Proceed as specified in the ''Standard 
Methods of Testing." Be sure to use the small needle of the 
Vicat apparatus. The specimen must be stored in the damp 
closet, as suggested in paragraph 37 of the reference. 

2. With the Gillmore Needles. Make the paste as above, and 
form it into a cake on a glass plate. Place the quarter pound 
needle on the cake and determine the length of time (from the 
moment of adding the water at mixing) when its surface will 
sustain the needle without making an appreciable indentation. 
This will be the time of the initial set. ]\Iake trials every 4 
minutes for 20 minutes ; after that, make a trial every 10 minutes 
until the initial set occurs, which will be from 30 minutes to 4 
hours. 



CEMENT LABORATORY 17 

Then, with the one poiincl needle, determine the time of the 
final set. This time also is counted from the moment of adding 
the water at mixing, and will be from i to 12 hours. 

Note : Be very careful that the needles are applied in a 
vertical position. There is usually some considerable time dur- 
ing which it is difficult to determine whether an indentation or 
surface mark has been made by the needle. Use form C-4. 

Experiment C-5. Constancy of Volume (Soundness) 

Reference: Standard Methods of Testing, paragraphs, 65-72. 

1. With a 500 gram sample of the cement mix a paste of nor- 
mal consistency, using the amount of water for mixing as 
determined for that particular brand of cement in Experiment 

C-3. 

2. Alake of this paste 4 pats and i ball. The ball should be 
about 154" in diameter. The pats must be made on perfectly 
clean and dry glass plates, entirely free from oil, and should be 
3'' in diameter and ^'' thick at the center, tapering to a thin 
even edge. 

3. Mark each pat and the ball with some distinguishing mark 
or number. Store all in the damp closet for 24 hours. 

4. After removing from the damp closet place one pat in the 
immersion tank, and one is to be stored away in air. These will 
be designated as the normal pats, since they are for the normal 
test. 

5. Place the two remaining pats on the upper screen of the boil- 
ing tank, and place the ball on the lower screen in the water. Boil 
for 3 hours, then examine for any sign of failure, which may be 
by crumbling, cracking, discoloration, warping, loosening from 
the glass, etc. Note these conditions in the report. This is the 
accelerated test. 

6. The normal pats must be examined at the end of i, 7, 14, 
21 and 28 days, and a record made of their condition. Use 
form C-5. 

Experiment C-6. Tensile Strength (Neat) 

Reference: Standard Methods of Testing, paragraphs 40-62. 

1. Oil the moulds and glass plates for 12 briquettes. This 
must be done before mixing the cement. 

2. Mix an 800 gram sample of the cement into a paste of the 
normal consistency and according to the standard method. Fill 
6 of the moulds quickly by the standard method. This is a very 



18 CEMENT LABORATORY 

important part of the operation, and absolute uniformity must 
be maintained throughout the whole proceedings. After these 
moulds are filled, mix another batch exactly like the first, and fill 
another set of 6 moulds. Number each briquette and record on 
Briquette Record sheet. 

3. Immediately after each mould is properly filled, and with it 
still remaining on its glass plate, place the whole in the damp 
closet to remain for 24 hours. 

4. After removing from the damp closet, remove all the 
briquettes from the moulds. Lay the first three aside to be 
tested. Place the remainder on edge in the immersion tank. 
Very thoroughly clean all the moulds and glass plates and slightly 
oil them; be careful of the edges. 

5. Test the three briquettes mentioned above, and record the 
results. These are the i day briquettes. 

6. At the end of 7, 14 and 28 days (from the time of making) 
test three of the briquettes that were stored in the immersion 
tanks. 

7. When testing the briquettes for tensile strength, be very 
particular about centering them in the clips of the machine. 
Apply a small initial load very slowly. All clip breaks must be 
indicated by the letter C in the report after the strength number. 
Use form C-6. 

Experiment C-7. Tensile Strength (Mortar) 

The proper consistency of mortars cannot be determined by 
the method used for determining a normal paste. The percentage 
of water to be used in mixing mortars is determined by the use 
of an emperical formula based upon the amount of water neces- 
sary for a normal paste of the cement, upon the proportions of 
cement and sand, and upon the character of the sand. Several 
such formulae are in use. Taylor's formula is as follows : 
X = per cent, of water to give the normal consistency for the 

sand mortar. 
A^ = predetermined percentage of water for a normal consistency 

paste of the cement to be used. 
72= parts of sand to one of cement by weight. 
.S^ = a constant depending on the consistency desired and the 
character of the sand. 
= 25. for Ottawa sand. 
= 30, for Standard Quartz sand. 
= 27 to 33, for Bar and Bank sands. 



CEMENT LABORATORY 19 

^ = — / (n ^ 1) Taylors formula 

1. Oil the moulds and glass plates for 12 briquettes. Make a 
I 13 mortar of the assigned cement and sand, using 250 grams of 
cement. The standard method must be used in mixing; that is, 
the cement and sand are to be thoroughly mixed dry, then the 
amount of water (as determined by Taylor's formula) is to be 
added and mixed as in Experiment C-^. Fill 6 of the moulds 
with this mixture. 

2. I\Iake a I :2 mortar as above, using 300 grams of cement, 
and fill the other 6 moulds. 

3. Place all in the damp closet for 24 hours. Then remove 
from the moulds and store in the immersion tank until tested. 

4. Test 3 briquettes of each mixture at the end of 7 days and 
28 days. 

5. When making the briquettes, place a thin coating of neat 
cement paste on one face of one large end of the briquette. After 
removing from the moulds, the briquettes may be marked on this 
smooth surface with a lead pencil. Use form C-6. 

Experiment C-8. Compression Strength (Neat and Mortar) 

1. Oil the moulds and glass plates for eight 2'' cubes and four 
i"' cubes. Weigh out 500 grams of the cement and mix into a 
normal paste. (See results of Experiment C-3.) Fill the i'' 
cube moulds with this paste. 

2. Mix a I :2 mortar of the cement and sand, using 500 grams 
of cement. (See Experiment C-7.) Fill four of the 2'' cube 
moulds with this mortar. 

3. ]\Iix a I 13 mortar of the cement and sand, using 300 grams 
of cement, and fill the other four 2" cube moulds. 

4. All are to be placed in the damp closet for 24 hours, then 
removed from the moulds and placed in the immersion tank until 
tested. 

5. Test 2 of each kind of the 2" cubes and 2 of the i'' cubes at 
the end of 7 days and 28 days. Use data form C-8. 

Experiment C-g. Modulus of Rupture 

The determination of the modulus of rupture is sometimes 
made instead of the tensile strength, and it is made by breaking 
a small beam (i'' x i'' x 12''), supported at the ends and loaded 
at the center. 

The formulae for bending moment and resisting moment of 



20 CEMENT LABORATORY 

beams give the theoretical stress on the extreme fiber when the 
material is not stressed beyond its elastic limit. These formulae 
are used, however, to obtain the probable value of the stress on 
the extreme fiber when the stress is known to be beyond the 
elastic limit and at the point of rupture; the value of the stress 
thus obtained is called the modulus of rupture. 

Let wS" represent the modulus of rupture ; W, the load in pounds 
concentrated at the middle of the beam ; /, the length of the beam 
in inches between the supports ; b, the width in inches ; d, the 
depth in inches ; then in pounds per square inch 

It should be understood that this test for the modulus of rup- 
ture does not, by any means, give so reliable an indication of 
the strength of cement as does the test for tensile stress, and 
neither are the results equal. But for obtaining experimental 
data in certain investigations, and for comparative and approxi- 
mate tests, this test for the modulus of rupture is sometimes made. 

1. Make six beams and six briquettes of neat cement. This will 
require two batches of 1,500 grams each. Store in the damp 
closet for 24 hours, then remove from the moulds and store in 
the immersion tank until tested. Test at 28 days old. 

2. Make beams and briquettes as above, using a 1 13 mortar. 
Test at 28 days old. Compare the modulus of rupture and the 
tensile strength. Use data form C-9. 

Experiment C-io. The Variation of Tensile Stress with 
Amount of Mixing Water 

1. Make three briquettes of neat cement, using the amount of 
water necessary to give a normal paste. 

2. Make three briquettes of neat cement, using two per cent. 
less water than required for the normal paste. 

3. Same as (2), except using four per cent, less water than 
normal. 

4. Same as (2), except using six per cent, less water than 
normal. 

5. Same as (2), except using two per cent, inore water than 
normal. 

6. Same as (2), except using four per cent, more water than 
normal. 



CEMENT LABORATORY 21 

7. Alake the same number of briquettes as above of a i 13 
mortar, beginning with the amount of mixing water necessary 
for the normal mortar. Then reducing and increasing the amount 
of water, as in 2, 3, 4, 5, and 6. 

8. Store all in the damp closet for 24 hours, then in the immer- 
sion tank until tested. Test all at 28 days. 

9. With the results of the tests plot a curve for the neat 
briquettes, and a curve for the mortar briquettes. Plot J\Iean 
Tensile Strength as ordinates,and Percentage of ^lixing Water as 
abscissae. Alark for each curve the ordinate showing the strength 
of the normal briquettes. Use data form C-io. 

XoTE : Be very particular to use the same method in forming 
all the briquettes in the moulds. 

Experiment C-ii. Effect of Different Methods of Moulding 
on the Tensile Strength of Briquettes 

Alake three briquettes of a normal paste (or mortar as as- 
signed) in each of the following six ways: 

1. Fill the moulds heaping full and press in place with the 
two thumbs, making just three presses for each briquette, then 
cutting off the surplus and smoothing down with the trowel; do 
not turn them over. > 

2. Same as i, except turn the moulds over and heap on more 
paste (or mortar), press in place and trowel as before. 

3. Fill the moulds by three layers, pressing each layer in place 
with the thumbs, as above, then cutting oft" and smoothing sur- 
face with the trowel ; do not turn them over. 

4. Fill the moulds loosely heaping full, and, without pressing 
with the thumbs, force the cement (or mortar) in place with the 
flat of the trowel, then cut off and smooth the surface. 

5. Fill the moulds loosely, a little at a time, and with a hard- 
wood rammer (about Yx" in diameter with square end) ram the 
paste in place until full, then trowel the surface. Use the rammer 
in such a way that it does not tend to further mix or work the 
paste, but only to ram it in place. 

6. Fill the moulds half full and press in place with a rammer 
the form of the briquette, fill full and ram in place again, then 
trowel the surface. 

7. Store in the damp closet for 24 hours, then in the immersion 
tank until tested. Test at 28 days. Use form C-ii. 



22 CEMENT LABORATORY 

Experiment C-12. Tests of Sand 

The results of tests on cement mortars depend very largely 
upon the character and condition of the sand used. Hence, the 
desirability of using a standard sand in all standard tests, and 
especially where the results obtained in different laboratories are 
to be compared. 

In this country a standard sand is that recommended by the 
American Society of Civil Engineers (in 1885). It is an arti- 
ficially prepared crushed quartz, of such fineness as to pass a 
number 20 sieve and be retained on a number 30. A later Com- 
mittee of this same Society recommends the use of a natural 
sand from Ottawa, 111., of the same fineness as the quartz sand. 
This latter is a silicious sand, with almost spherical grains, and 
gives strength tests 20 to 30 per cent, higher than similar ones 
from the quartz sand. 

The local bar and bank sands are sometimes used in testing, 
but their values vary very widely on account of their purity, 
fineness, specific gravity, percentage of voids, and shape of the 
grains. The tests for determining these qualities are the regular 
routine tests, and are outlined as follows : 

1. Purity. This test, when completely carried out, is a chem- 
ical analysis. But the usual test is for the determination of clay, 
loam, organic matter, and other extraneous materials. The 
general opinion is that small percentages of clay and mineral 
matter are not deleterious, while loam and organic may be. 
These impurities are all determined at once by elutriation, and 
generally classified as loam. 

The method is simply to weigh out 50 grams of the sand, 
place in a beaker or settling jar and add 200 to 300 c.c. of water 
and stir vigorously. Then allow to settle for 15 seconds and 
decant. Repeat until the water remains clear after stirring. Pour 
off the water and dry the sand in the drying oven until perfectly 
dry, then weigh. The loss is the amount of loam, and should be 
stated as a percentage of the original weight. A check deter- 
mination should always be made. 

2. Fineness. This is determined by weighing out 100 grams 
of the sand and sifting through a nest of sieves of the following 
sizes: 10, 20, 30, 40, 50, 75, 100, 150, and 200. The percentage 
retained on each sieve is determined. 

A graded sand will, in general, give higher results on the 
strength test than an all coarse or all fine sand; and a coarse 



CEMENT LABORATORY 23 

sand higher than a fine sand. Plot a curve with percentages as 
ordinates and sieve numbers as abscissae. 

3. Specific Gravity. Dry a 55 gram sample of the sand and 
introduce into the Le Chatlier flask, the same as for determining 
the specific gravity of cement, excepting that water is used instead 
of benzine. 

Another method is to slowly pour lOO grams of the sand (pre- 
viously dried) into a glass graduate containing lOO c.c. of water. 
The additional volume shown in the graduate is the volume of the 
sand. The specific gravity may now be computed from the data 
thus obtained. 

The sand should be dried for one hour at a temperature of 
212° F., before use in either of the above methods. An average 
specific gravity of sand is 2.65. 

4. Voids. The sample should be dried before use. The specific 
gravity must be determined as above. Use a graduate or jar of 
known capacity, and determine the weight per c.c. of the dry 
sand. From this data compute the percentage of voids. 

5. Character of the Grains. The sand is examined under a 
lense or microscope, and is reported as round, smooth, sharp, 
angular, etc. 

6. Strength Tests. Mix six i-i briquettes each of the given 
sand and of the standard sand. Test at 28 days old. Compute 
the percentage of the given sand strength above, or below, the 
strength of the standard sand. Be careful to use the same method 
in forming the briquettes for each kind of sand. Use data 
form C-12. 

Experiment C-13. Effect of Size of Sand on Strength of Mor- 
tar 

1. Sift the sand through sieves so as to obtain the following 
gradings : 

L, large grains, passing a number 6 sieve and retained on a 
number 16. 

M, medium grains, passing a number 16 sieve and retained 
on a number 40 sieve. 

S, small grains, passing a number 40 sieve. 

2. Make 15 briquettes as follows: 
3 briquettes, i 13 of sand L. 

3 briquettes, i 13 of sand M. 
3 briquettes, i 13 of sand vS. 



24 CEMENT LABORATORY 

3 briquettes, i 13 of a mixture of sands consisting of i part L, 
I part M, and i part vS. 

3 briquettes, i 13 of a mixture of sands consisting of i part 
L, I part M, and 3 parts .9. 

3. Test at 28 days. Be sure to weigh each briquette just 
before testing. Use form C-13. Plot a curve with strengths as 
ordinates and weights of briquettes as abscissae. State con- 
cUisions. 

Experiment C-14. Effect of Fineness of Cement on Strength 

1. Make 6 briquettes of the cement (neat) as received, and 6 
briquettes i 13 mortar. 

2. Sift through a 200 sieve sufficient cement (in 100 gram 
lots) to make the following 24 briquettes. Sift until half of the 
cement has passed through. 

3. Make 6 neat briquettes, and 6 briquettes i 13 mortar, of the 
cement passing the 200 sieve. 

4. Make 6 neat briquettes, and 6 briquettes i 13 mortar, of the 
cement remaining on the 200 sieve. 

5. Break 3 neat and 3 mortar briquettes of each batch at 7 days 
and 28 days. State fully results and conclusions. Use form C-14. 



SEP 26 19n 



One copy del. to Cat. Div. 



\r 25 ' 



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